tow command problem
Thread Starter
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Tuned
Joined: Dec 2005
Posts: 348
Likes: 3
tow command problem
Ok heres the deal when i start the truck the controller goes through its diagnostic test turns on flashes the lights then turns off. but when i plug my trailer in it doesnt come on at all any idea whats going on. and yes the trailer does have electric brakes and they are hooked up. also if i pull the manual overide the controller turns on with a red trailer on it and the brakes on the trailer do not lock up. is there a relay somewhere that i should check or what. truck is a 06 f-250
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
I would start with seeing what the trailer plug sees. Make sure the correct pin has voltage when the brakes are applied. Then make sure that the trailer has a good ground and the brakes are pinned the same as the truck's plug. I've come across several trailers that were wired wrong.
The signal out from the brake controller is variable, so a relay would not be effective in delivering adjustable voltage.
The signal out from the brake controller is variable, so a relay would not be effective in delivering adjustable voltage.
Elder User
Joined: Aug 2007
Posts: 914
Likes: 1
From: Saskatoon, SK, CA
Your controller isn't recognizing a trailer attached if you get a red trailer sign when you push the manual brake activator. It should show a solid green trailer when you have connection. Problem could be in the trucks plug or wiring or in the trailer plug. Either way the controller doesn't see a trailer attached if you get the red trailer light. You should try hooking up another trailer that has electric brakes and see if the controller reacts properly just to make sure where to start looking.
Fleet Mechanic
Joined: Nov 2003
Posts: 1,372
Likes: 14
From: West Cornwall, CT
Fixing a trailer connection problem can be a lesson in frustration control. The best way is to find if the problem is with the truck or with the trailer by testing them seperately.
The plastic cover on the 7-pin trailer connection has a wiring pin-out diagtram on it. Try checking each output with a voltmeter and verify that each output works.
Next check the trailer end. I use a 12-volt battery and connect the battery negative side to the ground connection in the trailer's 7-pin connection. Then test each trailer pin to see if trailer lights, signals and brakes work.
If all else fails, Ford dealers have a test plug that connects to your truck's trailer connection. This tests the Tow Command system. With luck you can find the problem without visiting the dealer.
Usually it is a problem with trailer wiring. Either a shorted connection or poor ground.
Lou Braun
The plastic cover on the 7-pin trailer connection has a wiring pin-out diagtram on it. Try checking each output with a voltmeter and verify that each output works.
Next check the trailer end. I use a 12-volt battery and connect the battery negative side to the ground connection in the trailer's 7-pin connection. Then test each trailer pin to see if trailer lights, signals and brakes work.
If all else fails, Ford dealers have a test plug that connects to your truck's trailer connection. This tests the Tow Command system. With luck you can find the problem without visiting the dealer.
Usually it is a problem with trailer wiring. Either a shorted connection or poor ground.
Lou Braun
Thread Starter
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Tuned
Joined: Dec 2005
Posts: 348
Likes: 3
update: there is 12v at the 7 pin on the truck and when i pull the manual overide with the trailer plugged in there is 12v at the trailers junction box on the wires that go to the brakes but the tbc still does not turn on when the trailer is plugged in
Thread Starter
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Tuned
Joined: Dec 2005
Posts: 348
Likes: 3
anyone know if the cardone master cylinder from advance auto parts comes with the sensors installed on it the part number for advance is 103222 or does anyone know what the ford part number is for the master cylinder with the brake pressure transducer is.
New User
Joined: Aug 2008
Posts: 18
Likes: 0
Is there 12v all the way back at the brakes with the override on? Sounds like a ground problem.
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Tuned
Joined: Dec 2005
Posts: 348
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didnt get back that far didnt feel like takin the wheel off also the trailer does not use the frame as common ground everything that uses electric has a ground wire running to it from the junction box on the which gets its ground from the 7 pin on the truck. the ground is good at the junction box
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Tuned
Joined: Dec 2005
Posts: 348
Likes: 3
just checked voltage at the axle and there is 12 volts at the wiring that goes into the brakes on the axle i checked i didnt bother checking the other axle cause i know that at least one axle is wired properly and the controller is still not turning on with the trailer pluged in. also when i pull the manual slide it says check trailer
Senior User
Joined: Nov 2005
Posts: 312
Likes: 0
From: Western NC Mountains
What year is your truck? Some of the early O5 Tow Command units had problems and needed to be replaced with updated version. If I recall correctly the build date on the Tow Command Units that had problems were March of 04 or earlier. FYI, this is the build date for the unit NOT the truck.
Senior User
Joined: Sep 2007
Posts: 288
Likes: 0
Do not just figure its the truck with the problem it could be the wiring on the trailer. if thats not it, check all the fuses and relays associated with the tow command, there are seperate fuses and relays for lights, brakes, battery charge, ect...
FTE Legend
Joined: Jul 2005
Posts: 65,938
Likes: 1,432
From: Millersville, MD
How do you expect the emergency break-away to set the trailer brakes if you become disconnected if the trailer battery is NOT working/hooked up? BTW, do NOT test the breakaway switch with the trailer/truck cord plugged in....